I'm wondering if it is possible to hide the advanced view of a widget designer when using Feather. I've found instructions for Web Form designers here but cannot find anything with Feather.
Well everything runs in the context of your site, like your CSS should be able to modify things...however I had a peek and that button doesn't have any custom class to target it, it's not even the last-child.
I'm gonna submit as an issue
You can hide the Advanced button by defining a custom footer in your designer view: github.com/.../Overriding-the-default-widget-designer-buttons
Just tried it myself and it works like a charm. Hiding it via jQuery works as well of course, but this alternate solution might work out for you as well.